1. Field of Invention
This invention pertains to cutting devices for use in dental and orthopedic applications. More particularly, this invention pertains to a universal depth cut burr for use in shaping dental surfaces and/or skeletal surfaces, and methods of application thereof.
2. Description of the Related Art
In the fields of dentistry and orthopedic medicine, precise cutting and shaping instruments are frequently utilized such as drill bits and rotary cutting tools. For dental reduction and joint repair applications, efficient and compact cutting surfaces are required for drill bits and rotary cutting tools, which are referred to hereinafter as a cutting burr or a reduction burr. A cutting burr or reduction burr must provide a precise cut having a preferred width, length, and an exact depth of penetration for removal of material from surface(s) requiring reshaping. The exact depth of penetration is typically measured in 0.5 mm or 1 mm increments, which are not readily discerned by a practitioner's eye and hand coordination without mechanical assistance. A self-limiting cutting feature is preferred for limiting the depth of penetration and cutting in order to minimize removal of excess enamel or bone material. It is preferred practice to leave as much healthy enamel surface or bone surface as possible for bonding crowns or bone grafts thereto. A precise depth of penetration also protects underlying dentin, nerves and cell tissue.
In the field of dentistry, a frequently performed dental procedure includes the shaping and reduction of enamel on crown surfaces and lateral surfaces, either dentilingual or dentibuccal, of a decayed or cracked tooth. The operating space provided within a patient's mouth is extremely limited, and minimal changes in the tooth surfaces is preferred when reducing the enamel surfaces for bonding of a gold, porcelain, or ceramic cap thereon. For shaping of dental surfaces, a reduction burr is utilized that is elongated and presents a distal cutting surface that is rotated at high speeds of about 30,000 rpm while being positioned against the appropriate dental surfaces for reduction of the appropriate lateral and occlusal surfaces of the patient's tooth.
As in dentistry, the field of gnathoplasty requires precise cutting depth instruments are required for reconstructive surgery on a patient's jaw. Further, the field of orthopedics requires precise cutting depth instruments for shaping osseous surfaces in order to partially cut, elongate, and/or shape a patient's mandible, humerus, femur, tibia and fibula, or to reconstruct a patient's joint. Numerous prior designs have attempted to indicate the depth of penetration of the cutting or abrasive surface of a reduction burr by having depth indicia imbedded in the side of the burr. Unfortunately, if the operator of the reduction burr applies undue pressure on the shank of the burr, the working surface of the burr will readily penetrate past the preferred depth thereby cutting through additional enamel or bone, with a risk of cutting into internal tissue and nerves.
Typical of the prior art is a self-limiting occlusal surface reduction burr that includes a shank extended to a burr end, and having an intermediate conical flange of a diameter significantly greater than the diameter of the shank and burr end. Additional prior reduction burrs have an intermediate positioned flange that is typically triangular or rectangular in cross-section, and the depth of cut is determined by the distance between the burr end and the outer circumference of the intermediate positioned flange which rotates in unison with the burr end. Use of a reduction burr having an intermediate positioned flange of conical, triangular or rectangular cross-section is inherently limited to cutting applications against occlusal dental surfaces lacking steep cusps due to the increased cross-sectional width of the conical, triangular or rectangular flange. The width of an intermediate flange denies seating between steeply sloped cusps, denies seating on molar inclines, and denies insertion laterally between adjacent teeth while potentially cutting the adjacent tooth surface. Further, the outer circumference of a conical, triangular or rectangular flange will lacerate the gum tissue when the occlusal reduction burr is positioned at the gingival margins of a tooth. In addition, the width of the conical, triangular or rectangular flange is not utilizable against convoluted joint surfaces having limited widths therebetween. The dentist or orthopedic surgeon must frequently change to an elongated reduction burr bit having generally straight lateral sides without an intermediate flange to produce reduction cuts along dentilingual surfaces, dentibuccal surfaces and lateral surfaces between adjacent teeth, or for producing rows of cuts along ossiferous surfaces proximal of convoluted joint surfaces. Frequent changing of reduction burr bits between ones having intermediate flanges and bits having generally straight sides is time consuming, requires unpleasant inactive periods for the patient, and increases a risk of selection of reduction burr bits having inappropriate cutting depths other than the target depth of reduction. Further, if the perimeter of an intermediate flange, whether conical, triangular or rectangular in cross-section, is not perfectly concentric, then the rotational balance of the burr bit is disturbed with creation of vibration and wobble in the distal burr bit when rotated at 30,000 rpm or higher rpm. If vibration and wobble is present but not visible to the dentist or orthopedist, the vibration transmitted through the burr end can create fractures in the tooth enamel or in the ossiferous surfaces. A preferred method for reduction of dental or ossiferous surfaces is to operate a universal reduction burr having a configuration of a minimal diameter and providing a self-limiting depth of reduction of an abrasive burr end in order to reduce the shape of any sloped crown surface and lateral dental surface, or to cut into any convoluted ossiferous surface.
Prior reduction burrs typically include a depth limiting flange disposed perpendicular to the shank and perpendicular to the working surface of the burr end. A limitation to the use of a burr having a perpendicular flange is that the burr is not easily maintained in a level orientation when moved along the patient's convoluted lateral dental surfaces, therefore generating grooves in the enamel surface having uneven depths. Further, prior reduction burrs having perpendicular flanges of significantly larger diameter relative to the shank diameter and burr end diameter can easily obstruct the dental practitioner's view of the burr end during manipulation of a drill within the patient's mouth. Intermittent obstruction of a burr end during application against a dental surface by a significantly larger diameter perpendicular flange leads to mistakes in achieving optimal reduction depths for convoluted dental surfaces. Precise cuts with limited removal of enamel is preferred in order to minimally disrupt the remaining enamel surfaces.
A universal depth cut burr is needed that is sized to be rotatably connected to a dental drill and includes an abrasive burr end for cutting and shaping each enamel surface of a patient's crown and all lateral surfaces extended above the patient's gums. A universal depth cut burr is also needed that includes a burr end junction of a lesser diameter than an adjacent rounded shoulder for providing a self-limiting depth of penetration and providing unobstructed viewing of the burr end during reduction of any crown or lateral dental surfaces. A method of reduction is also needed for shaping any convoluted dental surface or convoluted ossiferous surface by utilization of a universal depth cut burr having a self-limiting junction of a minimal diameter disposed proximal of the burr end.